Genesis 17:19
“And God said, Sarah thy wife shall bear thee a son indeed; and thou shalt call his name Isaac: and I will establish my covenant with him for an everlasting covenant, and with his seed after him.”
KJV
Read in Genesis 17Meaning
God states that Sarah will bear a son named Isaac and that the covenant will continue through Isaac's descendants.
Read carefully
The distinction of Isaac's covenant role does not imply that Ishmael is worthless or hated, nor does it by itself settle modern ethnic or territorial disputes.
Reflection
The verse makes the narrative line precise while the wider passage preserves God's concern and blessing for more than one branch of Abraham's family.